262
FLIGHT International, 17 August 1967
PIPER TURBO NAVAJO
in the'Air. . .
The Navajo is a good-looking aircraft
by any standards. A pre-production
machine here flies over lonely Rockies
scenery where its far-ranging name-
sake Indian tribe may have roamed
the way to FL200. At gross weight, full rated power and a
speed of 110 m.p.h., an average climb rate of over l,200ft/min
is claimed. The Navajo felt nicely stable in the climb, which
even at 130 m.p.h. was at a modest attitude, and the noise level
on the flight deck was not at all obtrusive.
Having reached FL200, and settled on a north-westerly head-
ing from Kidlington, I checked a few sample cruise settings.
Seventy-five per cent power was tried first (2,400 r.p.m. and
33.5in manifold pressure) and a true airspeed of 250 m.p.h.
was recorded—a figure 10 m.p.h. in excess of the claimed speed
at gross weight. At 65 per cent power (2,400 r.p.m. and 28.4in),
236 m.p.h. was achieved (223 m.p.h. claimed), and 225 m.p.h.
(204 m.p.h. claimed) at 55 per cent power (2,400 r.p.m. and
24.3in). Even allowing for the fact that the evaluation flight
took place at nearly 1,0001b under gross, the lower power-
setting cruise figures are considerably more than the claimed
performance. Making a position-error allowance on the basis
of the curve in the pilot's notes left no reason to doubt this fact.
Although the American pilots' notes do not contain any
reference to permitted maximum or manoeuvring speeds, the
airspeed indicator of the demonstrator was green-lined to
210 m.p.h.—some 30 m.p.h. above the normal highest cruising
speed. At all cruising speeds the Navajo was impressive for
its easy gait; the controls gave a lively response for a moderate
effort, and the harmony between the axes felt good. The
trimmers are operated by sensibly sized wheels working in the
proper axes and with clear position indicators. The elevator and
aileron trimmers were powerful, but that for the rudder was
slightly less effective for quickly getting the slip-ball central.
A look at the low-speed characteristics started with a power-
off clean stall (the gear warning light flashes as power is
reduced and a warning horn sounds as speed falls off with
the gear up). At about 80 m.p.h. indicated airspeed the stall-
warning light—mounted above the attitude indicator—shone
and at 70 m.p.h. the nose dropped, accompanied by slight air-
frame buffet. In the same configuration, but in turning flight
in either direction, the stall was accompanied by buffet and the
aircraft rolled out straight.
Lowering of the undercarriage and flaps at the high permitted
speed of 150 m.p.h. was without significant trim change or
transient forces. As the stall was approached with everything
down, the warning light shone at an indicated 65 m.p.h. and
the nose dropped at the very low airspeed of 60 m.p.h. On
the several stalls I made in this configuration the wing dropped
quite sharply to port and only by very carefully checking that
the aircraft was flying absolutely straight (necessitating the
application of a fair amount of rudder as the speed decayed)
was it possible to do a stall without a significant wing-drop.
In view of this unexpectedly skittish performance I did not
feel inclined to try a stall off a turn in this configuration.
The book recommends a normal approach speed of 95-105
m.p.h. according to weight, or 85-95 m.p.h. for a short landing
technique, with full flap. The large powerful elevator was seen
to have good power at the mid-c.g. position of the flight, and
even at 85 m.p.h. the ailerons could induce a good rate of
roll. A simulated full-power overshoot from a trimmed
approach at 85 m.p.h. was easily held. With the aircraft trimmed
in a full-power climb at the placarded minimum control speed
of 85 m.p.h., the port engine was stopped unexpectedly for a
check on the assymetric handling. The aircraft proved very
controllable in this state, and nearly all foot load could be
trimmed out. Only the unfortunate tendency to drop a wing
at the all-down power-off stall is a blemish on an aeroplane
that otherwise handles finely at all speeds.
CANCELLED PROJECTS: THE LIST UP-DATED
DETAILS of aircraft, engine and missile projects cancelled
since 1951 were given by the Minister of Technology, Mr
Wedgwood Benn, in a written Parliamentary answer on July 28.
This latest list includes a figure of £2.5 million for the AFVG,
cancelled last month, and £0.26 million for the P35, the
"dynamic leap" vehicle on which British Aircraft Corporation
made a project study.
Estimated
Project Cancelled Expenditure
(£ million)
Transport Aircraft
Brabazon February 1952 6.45
Princess flying-boat May 1954 9.1
Vickers military transport December 1955 4.0
Rotodyne February 1962 13.65
HS68I February 1965 21.0
Operational Aircraft
Developed Sturgeon anti-submarine aircraft March 1951 0.5
D.H. fighter May I9S2 2.5
Developed Hawker Hunter July 1953 0.14
Swift February 1955 22.0
Swift photo-reconnaissance fighter June 1955 0.3
Swift crescent-wing research fighter December 1955 1.6
Avro rocket intercepter September 1955 1.0
Thin-wing Javelin June 1956 2.3
Fairey supersonic fighter March 1957 0.15
Supersonic bomber (including engine) March 1957 2.05
Naval inttfeepter December 1957 3.2
P.I 154 February 1965 21.0
TSR.2 February 1965 195.0
AFVG July 1967 2.5
Project
Engines
Nomad
Screamer
Soar
Turmo
Big Gyron
RB.I06
Orion turboprop
Scorpion
Spectre
Super Sprite
Missiles
Guided bomb with television eye
Vickers flying bomb
Air-to-ship guided bomb
Air-to-air missile with radar guidance
Long-range surface-to-air guided weapon
Heavy anti-tank missile
Blue Steel Mk 2
Bloodhound 3
Blue Streak
Low-level surface-to-air guided weapon
Medium-range surface-to-surface missile
Skybolt
Swingfire
Other
Balloon-borne early-warning radar
High-resolution reconnaissance radar
Lightning 3 auto-attack system
P35 aerial vehicle
Expenditure figures have been extracted
number of years and may noc all be on an idem
lations, estimates have been given. Both sets
approximate.
Cancelled
April 1955
March 1956
March 1965
March 1956
March 1957
March 1957
January 1958
February 1959
October I960
October I960
June 1954
September 1954
March 1956
June 1956
May 1957
September 1959
December 1959
March I960
April I960
December 1961
August 1962
December 1962
November 1964
Estimated
Expenditure
(£ million)
5.1
0.65
1.2
0.1
3.4
0.1
4.75
1.25
5.75
0.S5
3.1
0.7
0.9
7.5
1.5
2.4
0.825
0.6
84.0
0.8
32.1
27.0
0.234
1.3
0.73
1.4
0.26
November I960
February 1962
March 1965
October 1966
from records extending over »
:ical basis. For more recent <;*««'•
of figures should be